Plural temperature refrigerators



Dec. 18, 1956 F. F. FARMAIAN PLURAL TEMPERATURE REFRIGERATORS IN V EN TOR. 54/?006/9 F. FARMA/A/V BY ain- M, M9

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Filed Oct. 30, 1953 PLURAL TEMPERATURE REFRIGERATORS Fareugh Farman Farmaian, Philadelphia, Pa., assignor to Phiico Corperatinn, Philadelphia; Pa., a corporation of Pennsylvania Appiication fictober 30, 1953, Serial No. 389,430

9 Claims. (Cl. 62-1173) turesautoma-tically, andregardless of a wide'range'of' changes in ambient temperature.

It is now common practice to provide refrigerators :hav

ing separate compartmentswithin a single cabinet, for example separate freezing and'food storage compartments. Commonly each of these compartments is provided with evaporator means, and the apparatus includes suitable control means adapted to establish'fiow of refrigerant to both evaporators and, in accordance" with temperature conditions prevailingin the system, to terminate flow of refrigerant to one of the evaporators while: continuing flow of refrigerant to the other. In'certain machines of this type, the flow of liquid refrigerant is controlled in such manner as to cause one evaporator, usually the evaporator associated with the higher temperature food storage compartment, to cycle between a minimum temperature well below the freezing point of water; and

a maximum temperature sufficiently above freezing to permit melting and consequent removal of frost deposited upon said first evaporator.

Frequently refrigerators of this known type employ valve devices operating in conjunction with relatively complicated thermo-sensitive switches to achieve the desired distribution of refrigerant within the system. A novel and advantageous refrigerator of this latter type is disclosed and claimed in the co-pending"applicationof Malcolm G. Shoemaker, bearing Serial No. 296,995, filed July 3, 1952, now Patent No. 2,706,894, and assigned to the assignee of the present invention; Broadly, it is the primary objective of this invention to provide simpler and less expensive apparatus adapted to attain at least the major objectives achieved by the system of said pending disclosure.

In general it is an object of the invention to provideapparatus for effecting desired distribution of liquid refrigerant within a refrigerating system, automatieally.

It is also an object of the invention to provide a truly automatic refrigerant circulating systemf in'whi'ch distribution of liquid refrigerant to a'plurality of evaporators is effected automatically, and in am'anner'to maintain desired temperature conditionswithout the use of valves or' complicated controlled circuitry.

With special reference to the-utility of the invention in the field of refrigerators of the plural compartment type, it is an object of my inventionto modulate, -orcontrol Patent 2,774,223 Patented Dec. 18,1956

automatically, the supply of refrigerant to one of a pair of evaporators in accordance with ambient temperature, whereby the quantity of refrigerant delivered to the evaporator inthe warmer compartment very closely approximates that which is required to obtain optimum refrigerating temperatures therein throughout a wide range of ambient temperatures, and without substantially affecting the low temperature desired in the freezing compartment.

With more particularity it is an object of the invention to accomplish these general purposes by delaying how of liquid refrigerant, to the evaporator in the warmer compartment, during a portion of each on cycle of the refrigerating apparatus.

In achievement of the foregoing objects and advantages, and first briefly described, the apparatus of my invention includes novel thermal means effective to control the flow of refrigerant from the condenser to'the' evaporators of the system. This thermal means-is used in a system which includes areceptacle arranged to receive refrigerant flowing from the restrictor and which receptacle has a pair of spaced outflow passages, one of which leads to one path included in' the system, and the other of which leads to another path, said first path conducting refrigerant to the evaporator located within the freezer compartment and the other path conducting refrigerant to the evaporator positioned in the warmer compartment. Refrigerant'from both of said evaporators returns to the compressor through acommon suction line.

In particular accordance with the present invention,

the path leadingto the warmer evaporator is disposed in heat exchange relation with a body of material which presents considerable thermal mass and'whi'ch is exposed to ambient atmosphere and heated thereby. During initial operation of the apparatus liquid refrigerant flowing through the latter path is evaporated by heat exchange with the saidmass or body and thus only gaseous refrigerant is delivered to the evaporator loc'ated in the warmer compartment, until such time as sufii'cient heat isremovedfrom the said mass to cause its temperature to closely approach the temperature of the evaporating refrigerant; When this condition is reached evaporation of the liquid in' this path is discontinued and, thereafter,

liquid refrigerant flows into the evaporator of the warmer' compartment. The period of'delay, determined by the time required to cool the mass is a function of several factors, for example the thermal capacity of the mass and the ambient temperature to which it is exposed. It is understood of course that during operation of the system refrigerant will becontinuously fed to the freezer evaporator. In this way'the apparatus is effective to main tain desired'refrigerating temperatures in the two evaporator's over a relatively wide spread of ambient temperatures.

The manner in which the foregoing'and other objects and advantages may best be achieved will'be understood from a consideration of the following detailed description taken together with the accompanying drawings, in which'two embodiments, of the invention are illustrated. Inthedrawingst" I v Figure 1 is a diagrammatic view ofa plural evaporator refrigerating system incorporating. apparatus in accord- 10 'and'll cach'ofwhich'xis adapted to cool a separate zoneor's'pa'ce;asisrepresented at iZandlS'. Preferably,

food storage compartment of a household refrigerator whereas the space 13 comprises the low temperature freezing. compartment of such a machine. It .will be understood that the apparatus would be enclosed in a suitable insulated cabinet having partition means separating the aforesaid compartments.

In addition to the evaporators and 11 the system, in accordance with conventional practice, includes refrigerantcirculating means comprising compressor 14, and a condenser 15 from which liquid refrigerant flows toward the evaporators through expansion means of known type, for example through a capillarytube restrictor of the kind shown at 16. The restrictor delivers refrigerant to a suitable drier 17 from whence a mixture of liquid refrigerant and flash gas is delivered to an accumulator or receptacle designated generally by the reference numeral 18. From a point adjacent the top of accumulator 18 leads conduit 19 arranged to feed evaporator 11. From a point adjacent the bottom of accumulator 18 leads a conduit 20 which is arranged to conduct refrigerant to evaporator 10. Each of conduits 19 and 20 includes suitable restrictors' 21 and 22, respectively. The reason for this will be explained hereinafter. It will be understood that refrigerant delivered to evaporator 10 preferably,-

and as shown, flows through both evaporators in series, passing from evaporator 10 to evaporator 11 through conduit 23. The spent refrigerant returns to the compressor through suction conduit 24.

In particular accordance with the present invention a portion of refrigerant conduit 20 between accumulator 18 and restrictor 22 is disposed in heat exchange relation with a body of high thermal mass, which body may be of any suitable material capable of absorbing and retaining the desired quantity of heat necessary for efiicient operation of the system. Metals, for example, may be used for this purpose, as may certain solutions, particularly freezable solutions. 7

The mass 25 preferably is exposed to the ambient atmosphere, and the heat exchange between the mass and conduit 20 is a function of the length of the conduit in contact with the mass and of the difference in temperature between the circulating refrigerant and the ambient atmosphere. It should be understood, however, that heat may be applied directly to the mass 24 as by an electrical heating element, not shown.

During normal unmodulated operation of the abovedescribed apparatus, gaseous refrigerant flows from compressor 14 through condenser 15, wherein it is condensed and, as liquid, passes through restrictor 16, and drier 17 into accumulator 18 in which it separates by gravity into liquid and vapor, the liquid settling to the bottom and the vapor rising to the top of the accumulator. As mentioned above, restriction is introduced into the conduit 20 through which liquid refrigerant flows from the accumulator 18 toward the evaporator 10, as is indicated by the tubing of reduced size shown at 22, this restriction being provided in order that said conduit may be vapor blocked to afford modulation, as described hereinafter. As will be understood, presence of restriction in this conduit necessitates restriction of the upper conduit 19 (see the section 21) to prevent substantially complete bypassing of the lower conduit 20 and passage of the major portion of liquid refrigerant through the upper conduit. It will be recognized that such by-passingof the lower conduit is not desired except during initial modulated periods of operation when the heat exchange afforded by the thermal mass 25 is effective. a

When operation of thecompressor' is initiated gaseous refrigerant fiows through conduit 19 and passes directly into the freezer evaporator 11. Simultaneously, liquid refrigerant enters conduit 20 and, as it reaches thermal mass 24, is evaporated by the heat of the mass. The vapor thus formed passes into res'trictor 22 creating a vapor block at the entrance thereof. The resultant block substantially prevents flow of liquid refrigerant to evaporator 10 which is therefore not refrigerated. Under this condition the liquid level rises in accumulator 18, and

flow of liquid refrigerant established through conduit 19 from whence it passes directly to evaporoator 11. Evaporation of refrigerant at the thermal mass continues until the temperature of the mass is reduced to such an extent that transfer of heat is no longer possible. When this condition is reached, the vapor block is terminated and liquid refrigerant flows through restrictor 22 and into evaporator 10 to refrigerate the same.

The delay period, or length of time during which liquid refrigerant is prevented from flowing into evaporator 10, is influenced by several factors as mentioned above, such as the thermal capacity of the mass, and the ambient temperature. Also contributing to the delay is the restrictive value of restrictor 22, the discharge pressure of the refrigeration system, and the insulating value of the cabinet structure. It is understood, of course, that. by proper selection of these factors, the flow of refrigerant to evaporator 10 may be controlled to the desired degree, and in this way desired temperatures may be maintained at evaporator 10.

Control of compressor 14 is effected by a temperature responsive switch 26 having associated therewith a feeler bulb 27 so disposed as to render switch 26 responsive to the temperature at evaporator 10. It is to be understood that the bulb 27 may be associated in direct heat exchange relationship with either of the evaporators, or it may be disposed in the compartment somewhat spaced from the'evaporator, depending upon the requirements of the particular system. Any of these locations of feeler bulb 27 is contemplated by description of the device switch 26 as being responsive to temperatures at the evaporator.

'Ideally, and in the preferred system illustrated, the switch is set to cut in, or close and place compressor 14 across the line L, when the temperature at evaporator 10 reaches 36 F., thus to permit the evaporator to be completely defrosted during each off cycle. The circuit remains closed until the temperature at evaporator 10 is reduced to approximatelyv 0 F.

During tests of a system constructed in accordance with the invention, and using a two-compartment refrigerator of conventional design including the usual amount of insulation and a standard water load in the warmer compartment, under ambient temperature conditions varying between 65 and 110 F., the percentage of operating time varied between 23.7 F. at the lower ambient temperature to F. at the highest. The temperature of the water load within the warmer compartment varied only 2 while the evaporator in the freezing compartment maintained, within a few degrees, a temperature of 4 F. At the higher ambient temperature, when compressor running time was 100%, the delay in liquid refrigerant flow to evaporator .10 was only during the cycle initiating the continuous operation.

It will be understood that it is desirable to minimize the refrigerating effect of the evaporator disposed within the food storage compartment under conditions of low ambient temperature since, under these conditions, there,

although the delay time is longer for each individual pe-. riod of delay, the aggregate delay time is relatively short 7 since the unit tends toward steady operation rather than.

cycling frequently. In practice the accumulateddelay time at the lower ambient temperatures is considerable and operates to limit the refrigerating effect of the evaporator located within the main food storage compartment,

as compared with the refrigeratingeifect ofthat-evaporator under higher ambient temperatures, and the: desired modulation is therefore achieved.

It is, of course, obvious that the heat exchange relationship between conduit 20 and thermal mass 25 may take various forms. One such alternative arrangement is shown in FigureZ, wherein that portion of conduit 20 in heat exchange with the mass 25' is looped back upon itself so that two passes of the conduit'are in contact with the mass prior to its connection with restrictor 22'. Connecting the discharge end of the restrictor to evaporator is another conduit 28, also in heat exchange relationship with mass 25.

In this construction, as in that previously described, liquid refrigerant flowing through conduit will evaporate as it reaches mass which has previously been absorbing heat from the ambient atmosphere, and the resultant gas vapor blocks restrictor 22'. Evaporation continues until the temperature of the mass is reduced to a degree where further heat exchange is no longer possible, at which time liquid refrigerant flows into conduit 28. Due to the pressure drop across restrictor 22', refrigerant entering conduit 28 is at a lower temperature than refrigerant flowing through conduit 20'. Because of this, a certain amount of refrigerant will evaporate in conduit 28, thus further reducing the temperature of mass 25' with a resultant sub-cooling of refrigerant flowing through that portion of conduit 20 in heat exchange with mass 25 to such an extent that substantially pure liquid refrigerant flows through restrictor 22. As the amount of vapor in the mixture flowing through restrictor 22' decreases, the rate of liquid flow will increase, thus increasing the activity of evaporator 10'.

It will also be noted that if desired, and as illustrated in this figure, a portion of conduit 23 conducting refrigerant from evaporator 10' to evaporator 11 may be placed in heat exchange relationship with mass 25 and thereby sub-cool the refrigerant flowing therethrough prior to its entry into evaporator 11'.

From the foregoing description, it will now be recognized that by the present invention there is provided an inexpensive, truly automatic refrigerator of the multi compartment, multi-temperature type, in which the freezing compartment is maintained at a substantially con stant low temperature and the warmer food storage compartment is maintained at a substantially constant abovefreezing temperature, regardless of wide fluctuation in ambient temperature, and without the use of mechanical apparatus such as valves, etc. In addition, the apparatus effectively eliminates the defrosting problem normally encountered in such refrigerators,

The disclosed apparatus is of course subject to certain changes and modifications without departing from the es sential spirit of the invention. For example the described modulating means could be used to by-pass the evaporator means completely. In such event provision would be made (as by means of a suitable auxiliary heat exchanger) to re-evaporate the by-passed liquid refrigerant prior to return thereof to the compressor, pump. However it will be understood that such changes and modifications are contemplated as come within the scope of the appended claims.

I claim:

disposedto absorb .heat from the ambient: atmosphere duringperiods of idleness of said'circulating means, the construction and arrangement being such that'heat passes from said body to the. path disposed in 'heat exchange rela tion therewith and is eflective to evaporate liquidrefr'igerant flowing through the latter path whereby to vaporblock the same for the period of time, following initiation of operation of said circulating means,.required'to.

and further characterizedv by the inclusion:ofiaccumulator means arranged to receive refrigerant from said expansion means and from which refrigerantis supplied to said two paths, said accumulator means servingalso as means for separating vaporous from liquid refrigerant and for feeding said vaporous refrigerant through a predetermined one of said paths.

3. A refrigerating system in accordance with claim 1,- and further characterized in that one of said paths is provided with a convoluted portion, said body being associated in heat exchange relation with said portion.

4. A refrigerating system in accordance with claim 2, and further characterized in that one of said refrigerant flow paths communicates with said accumulator in an areaof vapor accumulation, said other path communicates therewith in an area of liquid accumulation, and said body is disposed in heat exchange relation with said last-mentioned path.

'5. In a refrigerating system of the type'including refrigerant circulating means, expansion means, and first and second evaporator portions, and in which system, under, one condition of operation, flow of refrigerant is from said expansion means through one passage leading I through said first and second evaporator portions in series and thence back to the circulating means, control means responsive to the temperature of an ambient medium and 7 effective to cause refrigerant to by-pass said first evapo- 1. In a refrigerating system of the type including re frigerant circulating means, expansion means, evaporator means, and means defining a pair of alternative flowpaths interconnecting said expansion means and said evaporator means, flow control apparatus effective to cause refrigerant to flow toward said evaporator means through one of said paths under one condition of operation, and effective to cause refrigerant to flow toward said evaporator means through the other of said paths under another condition of operation, said flow control means comprising: a body of material of relatively high thermal mass associated in heat exchange relation with one of said paths and being rator portion and to flow through another passage directly to said second evaporator portion under a modified condition of operation, said control means comprising: means for vapor-blocking said one passage under the said modified condition of operation, said last-mentioned means including a body of material relatively high thermal mass disposed in heat exchange relation with said one passage and normally containing heat at a temperature in excess of the temperature of liquid refrigerant within said one passage, the construction and arrangement being such that heat flows fromsaid body to said one passage upon initiation of operation of said circulating means and serves to volatilize liquid refrigerant flowing through said passage until the temperature of said body closely approaches the temperature of the refrigerant flowing through said one passage.

6. In a refrigerating system including expansion means adapted to feed liquid refrigerant, means defining a conduit to be fed from said expansion means-and including an evaporator, means defining an alternative conduit tobe fed from said expansion means and disposed 'to bypass said evaporator, and flow control means for transferring flow of liquid refrigerant from said first-mentioned contherein to vapor-block the same during the period of,

time required to cause the temperature of said body closely to approach the temperature of the refrigerant in the mentioned conduit.

7. A refrigerating system in accordance with claim 6, and further characterized in that said first-mentioned conduit is provided with an elongated restricted connection disposed between saidtbody and saidevaporator'.

8. A refrigerating system in accordance with claim 6, and further characterized by the inclusion of accumulator means arranged to receive refrigerant from said expansion means and from which refrigerant flows to said conduits, said accumulator means serving also as means for separating gaseous and liquid components of the refr'igerant flowing from said expansion means, said firstmentioned conduit communicating with said accumulator means in a region of liquid accumulation and said alternative conduit communicating therewith in a region of gas accumulation.

8 9. A refrigeratingsystem in accordance with claim 6, and further characterized in that said body is adapted and disposed to absorb heat from the ambient atmosphere during'peri ds' of idleness of said refrigerating system.

References Cited in the file of this patent 7 UNITED STATES PATENTS 

